Rep. Mike Gallagher (R-Wis.) said he will not serve out the remainder of his term in the U.S. House and will instead resign in mid-April, cutting House Republicans’ already narrow margin over Democrats even further.

“After conversations with my family, I have made the decision to resign my position as a member of the House of Representatives for Wisconsin’s Eight Congressional District effective April 19, 2024,” Gallagher said in a post on social media Friday.

Gallagher is the second House GOP member in recent weeks to say he won’t even serve out the remainder of his term and will instead quit Congress midsession. Rep. Ken Buck (R-Colo.) said he would not seek reelection and then moved up his resignation date to Friday.

After Buck’s resignation takes effect, there will be 218 Republicans and 213 Democrats in the House, with four vacancies. That is the bare minimum for a majority in a fully seated, 435-member chamber.

With Gallagher’s departure, the number of Republicans would fall to 217. Two seats are expected to be filled soon: a historically Democratic one in New York in late April, and a GOP one in California in May.

This combination would mean that, from mid-April to May, House Republicans could afford only one defection on party-line floor votes and still win them. With the vagaries of members’ illnesses, family obligations and other situations, which party could actually muster a majority on any given day would be up in the air.

Gallagher, who just turned 40 in early March, was considered an up-and-comer in his party, having notched a committee chairmanship with the top spot on a bipartisan panel examining the United States’ strategic competition with China.

He said that he had already consulted with House Speaker Mike Johnson (R-La.) and looked forward to seeing Johnson name a new chair.

Quitting Congress in the middle of a session, or with the end in sight around the turn of the final year, is a relatively rare occurrence. But a recent Washington Post analysis of members quitting found the pace of departures at the highest in at least four decades.

In addition to Gallagher and Buck, other members who have quit early included David Cicilline, a Rhode Island Democrat; Brian Higgins, a New York Democrat; Bill Johnson, an Ohio Republican; and Chris Stewart, a Utah Republican.

Most of them had other employment already lined up. And the grind of the U.S. representative job — which entails weekly flights to and from Washington, endless fundraising, and day-to-day work in Washington in a sharply polarized environment — can wear on members.

But Gallagher looked on the bright side in his statement Friday.

“Four terms serving Northeast Wisconsin in Congress has been the honor of a lifetime and strengthened my conviction that America is the greatest country in the history of the world,” he said.